Interpretive Summary: Certain lupines (Lupinus spp.) contain alkaloids that cause contracture-type skeletal birth defects and cleft palate ('crooked calf syndrome') if the pregnant cow consumes them during the 40 ' 70th day of gestation. The objective of this study was to determine when cattle graze velvet lupine (Lupinus leucophyllus Dougl.) and whether this period overlaps the critical period of gestation. In the Channel Scablands of eastern Washington, cows consumed lupine during July and August after cheatgrass and other forbs matured, while the deep-rooted lupine remained green and succulent. This period of lupine consumption overlapped the critical period of gestation, but no crooked calves were produced, due to the reduction in lupine density and subsequent limited consumption. It is recommended to restrict cows' access to lupine during July in years when lupine density is high.

Technical Abstract:
Certain lupines (Lupinus spp.) contain alkaloids that cause contracture-type skeletal birth defects and cleft palate ('crooked calf syndrome') if the pregnant cow consumes them during the 40 - 70th day of gestation. The objective of this study was to determine when cattle graze velvet lupine (Lupinus leucophyllus Dougl.) and whether this period overlaps the critical period of gestation. The grazing studies were conducted in 2001, 2002 and 2003 in the same 100 ha pasture in eastern Washington. In 2001 the amount of lupine consumed was compared between 2 groups of cows: 1) five cows with crooked calves at their side, 2) six cows with normal calves. There was no difference in the amount of lupine consumed between groups (P = 0.15), and all cows consumed some lupine. In 2002, ten cows (different from those used in 2001) with normal calves were used, and in 2003, eight of the same cows from the 2002 study with normal calves were used. In all three years cows started consuming lupine in July and August after cheatgrass dried and annual forbs matured. Lupine is a deep rooted perennial which remained green and succulent longer into the summer than the associated forages. While the patterns of lupine consumption were similar between years, the amount of lupine consumed differed among years (P < 0.0001) ranging from 7 to 24% of bites at peak consumption. Lupine consumption occurred during the critical period of gestation in 2 of the 3 years, but no crooked calves were produced.